1. Field of Invention
The present invention relates to the separation of minor amounts of impurities from organic products such as glycols, glycol ethers, hydrocarbons and the like by an improved distillation procedure.
2. Description of the Prior Art
During normal preparation procedures, various oxygenated derivatives of organic products such as glycols, glycol ethers, glycol ether esters, hydrocarbons and the like, are formed in very small amounts especially at the elevated distillation temperatures which are normally employed in the production of such products. These impurities are frequently aldehydes, ketones, acids and the like and are undesirable in the product in that they impart characteristics such as malodor to the product.
Various methods are known for separating minor amounts of impurities, especially close boiling impurities, from various products including azeotropic and extractive distillation procedures but such prior methods are generally complicated and expensive. Steam stripping techniques have been employed but tend to result in the introduction of unwanted impurities with the steam, as well as producing water enriched products.
Stripping with inert gas, eg. nitrogen, produces a non-condensible stream which, if vented to the atmosphere would add to pollution, and if flared, adds a large load to the flare system. Also the inert gas does not enhance the volatilities of impurities.
Now, in accordance with the present invention there is provided a simple and effective distillation procedure whereby the separation of minor amounts of impurities is achieved.
In accordance with the invention, the organic mixture to be purified is fed to the upper section of a fractional distillation column, while a stripping component such as water or methanol in liquid form is fed to the column with the organic mixture to be purified or at a point below the point of introduction of the mixture to be purified. A reboiler is provided wherein bottoms from the column is vaporized and circulated to the column thus providing heat to the column. Heat input into the column via reboiler vapors is sufficient to ensure vaporization of the liquid stripping component stream introduced to the column, and the pressure maintained in the column is effective to prevent overheating especially in the reboiler, while maintaining stripping vapor flow upwardly through the column. The stripping component, eg. water, plus the undesirable impurities are removed overhead, organic product substantially reduced in impurities is removed as bottoms.